Electromagnetic interference (EMI), also called radio-frequency interference (RFI) when in the radio frequency spectrum, is a disturbance generated by an external source that affects an electrical circuit by electromagnetic induction, electrostatic coupling, or conduction. The disturbance may degrade the performance of the circuit or even stop the circuit from functioning properly. In the case of a data path, these effects can range from an increase in error rate to a total loss of the data. EMI can also affect mobile phones, FM radios and televisions.
Surface-mount technology (SMT) is a method for producing electronic circuits in which the components are mounted or placed directly onto the surface of printed wiring boards (PWBs), which may also be referred to as a printed circuit board (PCB). An electronic device so made is sometimes referred to as a surface-mount device (SMD) or an SMT device. SMT has largely replaced the through-hole technology construction method of fitting components with wire leads into holes in the circuit board.
A Faraday cage or Faraday shield is an enclosure used to block electromagnetic fields. A Faraday cage may be formed by a continuous covering of conductive material or in the case of a Faraday cage, by a mesh of such materials. A Faraday cage operates because an external electrical field causes the electric charges within the cage's conducting material to be distributed such that they cancel the field's effect in the cage's interior. In some situations, Faraday cages are employed to enclose devices that produce RFI, such as radio frequency (RF) components, such as transmitters, amplifiers, couplers, etc. to prevent their radio waves from interfering with other nearby equipment, including components mounted on the same PWB.